Numerical analysis of rock cover thickness of subsea tunnel

Since the first subsea tunnel - Kanmon tunnel was built in 1936 in Japan, there have been nearly 100 subsea tunnels constructed all over the world. Under special environmental and geological conditions, subsea tunnels are the safest and most economical scheme. The demand for constructing a subsea tunnel is very necessary and imperative in Xiamen, an island in south-east China. After it is constructed, it will be the first subsea tunnel in PR China. The highway tunnel will have double-lines, each line will be about 6000 m long and have three running lines. The cross section of each tunnel is about 14.7 m width and 9.85 m high, the area is about 100 m2, the maximum inclined angle is 3.5% and the design altitude is -70 m. The distance between the central lines of the two tunnels is about 50 m. Drill-blast excavation method will be adopted. Engineering analogical analysis and numerical analysis are used in the tunnel design. For different design altitude, comparison of the rock cover thicknesses in several key cross sections with Norway subsea tunnel experience formula is plotted in Fig. 1. Through the figure, it is very clear that, for most cross sections, if the design altitude is elevated 8.0 m, the rock cover thickness will satisfy the Norway experience formula, but for position K8+750, special reinforcement is needed. Many numerical models are also adopted for analyzing, include different design altitude, different initial geo-stress. Fast Lagrange method is used and solid-fluid coupling is considered. Through numerical analysis, the fluid flow tends to be stable in 70 days after excavation. The tunnel is on the whole stable if original +4.0 m scheme is adopt, but in section K8+750, there are thicker strongly weathered layer, the influence of fluid flow is notable. (A) "Reprinted with permission from Elsevier". For the covering abstract see ITRD E124500.

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  • Authors:
    • QIU, X B
    • LI, S C
    • CHEN, W Z
  • Publication Date: 2004-7

Language

  • English

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Filing Info

  • Accession Number: 01011596
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Dec 19 2005 3:19PM